This invention relates generally to pipeline pigs which travel through an interior of a pipeline and service and maintain the pipeline. More particularly, the invention relates to pigs used to dewater a multi-phase or predominantly gas pipeline in which liquids are present and disperse inhibitor within the line.
In multi-phase gas production pipelines, or similar systems in which liquids are present in a predominantly gas pipeline, a need often exists to push out only a small portion of the liquids in order to prevent overrunning limited capacity processing equipment or slug-catchers. For example, in high liquid-hold-up pipelines with slug-catching or process over-run limitations—or in applications in which top of the line corrosion requires inhibitor treatment—moving conventional pigs and/or spray pigs through the line causes process upsets or slug-catcher overrun because these pigging solutions (for liquid removal or inhibitor application) push most or substantially all the liquid out of the pipeline in a single pass. In many cases, use of these pigs involves complete shutdown, partial shutdown or other more costly operating scenarios.
The invention disclosed herein provides an operating scenario solution in lieu of conventional pigs or expensive pipeline system re-design—such as installing larger slug-catchers, using smaller diameter pipeline to achieve an annular versus stratified flow regime, or deploying expensive processing equipment—while avoiding process upset costs and maintaining normal production rates and revenue streams.